1. Field of the Invention
The present invention relates to a piezoelectric actuator, a liquid transporting apparatus, and a method of manufacturing liquid transporting apparatus, and in particular to a piezoelectric actuator, a liquid transporting apparatus, and a method of manufacturing liquid transporting apparatus in which a cross talk between a plurality of operating sections is reduced.
2. Description of the Related Art
An ink-jet head which discharges ink from a nozzle onto a recording paper is an example of a liquid transporting apparatus which discharges liquid onto an object subjected to discharge. This ink-jet head includes a channel unit which has an ink-discharge channel including a pressure chamber which communicates with the nozzle, and a piezoelectric actuator which causes an ink to be discharged from the nozzle by changing a volume of the pressure chamber. In this case, a general piezoelectric actuator includes a vibration plate which is positioned oppose to the pressure chamber, a piezoelectric element which is formed of a material such as lead zirconate titanate (PZT) and arranged on a surface of the vibration plate, and an individual electrode which is formed in an area facing the pressure chamber on a surface of the piezoelectric element. The piezoelectric actuator is structured such that when a drive voltage is applied to the individual electrode, an electric field is generated in the piezoelectric element positioned corresponding to the individual electrode, the piezoelectric element and the vibration plate are deformed partially so as to apply pressure on ink in the pressure chamber.
In such ink-jet head, for realizing both of high quality of recording image and the reduction of the size of the head, there is a tendency that a plurality of nozzles are arranged closely. However, when an attempt is made to arrange a large number of nozzles very closely, it is necessary to arrange a plurality of pressure chambers closely, too. Therefore, when a voltage is applied to an individual electrode facing a certain pressure chamber and the piezoelectric element to deform the vibration plate, this deformation is propagated even to a piezoelectric element and a vibration plate of an area corresponding to an adjacent pressure chamber, which in turn causes a phenomenon (a so-called cross talk) which destabilizes the ink-discharge characteristics of a nozzle communicating with the adjacent pressure chamber. As a result the negative effect exerted on a printing quality cannot be neglected. More specifically, due to the cross talk, there is an increased variation in a speed of the ink droplet discharged from each of the nozzles or a decrease of discharge stability.
In view of the situation, an ink-jet head is disclosed in Japanese Patent Application Laid-open No. 2-187352 and Japanese Patent No. 3152260. In this ink-jet head, a groove is formed by a dicing process in an area of the piezoelectric element and the vibration plate, which does not overlap with the pressure chamber, with the piezoelectric element joined to a surface of the vibration plate, so that the deformation of the piezoelectric element and the vibration plate is hardly propagated between the adjacent pressure chambers.
Japanese Patent Application Laid-open No. 2-187352 discloses laminating a piezoelectric element on the vibration plate before forming a groove in the vibration plate and cutting the piezoelectric element and the vibration plate simultaneously so that the groove is formed in the vibration plate. The obtained head has a structure in which the piezoelectric element is divided into individual piezoelectric elements with a plurality of the grooves intervening therebetween in the vibration plate, as shown in FIGS. 1 and 2 of this patent document.
Japanese Patent No. 3152260 discloses, to prevent the cross talk, laminating the vibration plate and the piezoelectric element on the pressure chamber and then cutting simultaneously the piezoelectric element and the vibration plate so that a groove is formed which extends to a side wall of the pressure chamber. The obtained head has a structure in which not only the piezoelectric element but also the vibration plate are divided for each of the pressure chambers, as shown in FIGS. 1 to 4 of Japanese Patent No. 3152260.